General Science GK Questions with Answers – Page 83

For small swings the time period is T = 2π√(L/g), which contains the length and gravity but neither the mass nor the amplitude.

Apical meristem sits at the growing tips of stems and roots, and its dividing cells make them longer. Meristems are groups of cells that keep dividing throughout a plant's life.

HIV spreads through body fluids such as blood, semen, vaginal fluid and breast milk, not through droplets from coughing, sneezing or talking.

Moving a substance from low to high concentration is uphill work, and the cell pays for it with ATP.

Ribosomes stuck on the outer surface of the endoplasmic reticulum give it a grainy, rough look under the electron microscope.

An ion-exchange resin or zeolite swaps the calcium and magnesium ions that cause permanent hardness for sodium or hydrogen ions.

Smooth muscle is a muscular tissue, one of the four basic animal tissues, not a connective tissue. Animal tissues are of four kinds: epithelial, connective, muscular and nervous.

Copper in the +1 state is reduced to metal, so it is the oxidant; sulphur of Cu2S is oxidised, so it is the reductant.

The RER is studded with ribosomes, the actual sites where amino acids are joined into proteins. Ribosomes read the message carried by mRNA and link amino acids in the right order.

A medium more concentrated than the cell is hypertonic, so water leaves the cell by osmosis. In osmosis water moves across a selectively permeable membrane from the side with fewer dissolved particles to the side with more.

Aerenchyma is a kind of parenchyma whose cells enclose large air-filled spaces. These air cavities keep aquatic plants such as water hyacinth, lotus and Hydrilla afloat and let oxygen move down to roots and stems that sit in waterlogged soil or under water.

Together the two resins take out every dissolved ion, which leaves demineralised water. In the cation exchange resin (written RH), metal ions such as Ca2+, Mg2+ and Na+ are swapped for H+ ions.

Radiation carries heat as electromagnetic waves, and these waves travel even through empty space. Heat moves in three ways.

This is the incorrect statement, because periodic motion repeats after every interval T, again and again. The time period T of a pendulum is the time for one complete oscillation, that is, the smallest interval after which the bob returns to the same position moving in the same direction.

These are the three places in a eukaryotic cell where DNA is found. The nucleus holds nearly all of a cell's DNA, packed with proteins into chromosomes.

A ribosome contains RNA, but it has no genes of its own; it reads messenger RNA sent from the DNA of the nucleus or an organelle.

A chemical reaction produces only internal forces, which cannot change the motion of the centre of mass but can change internal kinetic energy.

Water is densest at 4 °C, where one cubic metre has a mass of almost exactly 1000 kg.

Latent heat is absorbed during a change of state while the temperature stays fixed. When water boils at 100 °C, adding more heat does not raise its temperature; the energy goes into breaking the attractions between molecules so that liquid turns into vapour.

The stone takes 2 s to fall 20 m, and in that time it moves 12 × 2 = 24 m sideways.